1. Field of the Invention
The present invention relates to an organic light emitting diode (OLED) display device and a method of driving the same.
2. Discussion of the Related Art
Each of a plurality of pixels included in an organic light emitting diode (OLED) display device includes an OLED including an organic light emitting layer between an anode and a cathode, and a pixel circuit for independently driving the OLED. The pixel circuit primarily includes a switching thin film transistor (TFT), a capacitor, and a driving TFT. The switching TFT charges the capacitor with a data voltage in response to a scan pulse and controls a current amount supplied to the OLED according to the data voltage charged in the driving TFT to adjust a light emitting amount of the OLED.
However, in the OLED display device, the characteristics such as threshold voltage Vth and mobility of a driving TFT may be different per pixel due to process deviation and so on and thus, current amounts for driving the OLEDs are different, thereby causing luminance deviation between pixels. In general, problems arise in that a characteristic difference of an initial driving TFT causes display spots or patterns and a characteristic difference caused by degradation in the driving TFT during driving of the OLED reduces a lifespan of an OLED display panel or generates an afterimage.
To overcome these problems, a timing controller senses a threshold voltage and mobility of a driving TFT of each pixel using a data driver and compensates data supplied to each pixel according to the sensed threshold voltage and mobility of the driving TFT, which has been introduced before. However, problems arise in that, when a compensation data voltage is calculated using this method, if the calculated compensation data voltage exceeds a maximum voltage that can be driven by the data driver, it is difficult to compensate data.